Electromagnetic converters are known in many embodiments, for example as generators. The power supply for electrical or electronic circuits, in particular very small circuits or small electrical circuits in small and very small appliances or control elements, such as radio switches or radio sensors, is frequently formed by battery power and/or solar energy, rechargeable batteries or the like. One disadvantage of this way of supplying power to small or miniaturized circuits or small components is that the energy supplier, e.g., the battery or the rechargeable battery, often occupies a large amount of space which the actual electronic circuit occupies, thus destroying the space advantage obtained by miniaturization. This also applies to the use of solar cells for supplying electrical power to circuits such as these. The size of the solar cells is many times greater than the size of the electronic circuit thus, in this case as well, destroying the space advantage obtained by miniaturization, and often the weight advantage as well. A further significant disadvantage of a power supply such as this is that, particularly when these systems are equipped with a power supply with battery or rechargeable battery backup, they are not maintenance-free. This is because, in particular, batteries and rechargeable batteries are subject to ageing, and must be replaced at predetermined time intervals. For example, a radio switch, such as that which is known as a control element for a radio-controlled motor vehicle locking system, contains a power supply in the form of a rechargeable battery or a battery in addition to its electronic components, which form the radio technology and a switching contact. The switch and the rechargeable battery may actually be those components which occupy the greatest amount of space in this small appliance. The proportion of the weight of these two components may also be considerably greater than that of the electronic circuit. Furthermore, the rechargeable battery must store energy during the time in which the radio switch is not being used as well, which energy is not required at this time and is kept available as stored energy.